Multi-bend steerable mapping catheter

ABSTRACT

An electrophysiology catheter introduced through the groin and inferior vena cava into the right side of the heart comprises an elongate flexible shaft having a steerable distal section and a prolapsing section located proximally of the distal section. The distal section is inserted into the coronary sinus and a back-steering force is applied to the catheter to anchor the distal section therein, after which the catheter is further advanced to prolapse the prolapsing section against the high right atrium. Electrical pathways in both the coronary sinus and the high right atrium are mapped using respective electrode pairs carried on the distal and prolapsing sections of the catheter.

RELATED APPLICATION DATA

The present application is a continuation of U.S. patent applicationSer. No. 13/557,038, filed Jul. 24, 2012, now U.S. Pat. No. 8,423,115;which is a continuation of U.S. patent application Ser. No. 12/838,285,filed Jul. 16, 2010, now U.S. Pat. No. 8,229,538; which is acontinuation of U.S. patent application Ser. No. 11/470,132, now U.S.Pat. No. 7,774,039, the entire disclosures are incorporated herein byreference.

FIELD OF INVENTION

This invention pertains to electrophysiology (“EP”) mapping cathetersand, more particularly, to a multi-bend, steerable catheter configuredfor accessing and mapping the high right atrium and coronary sinus viagroin access and the superior vena cava.

BACKGROUND

Electrophysiology is the study of electrical impulses through the heartand is focused primarily on diagnosing and treating arrhythmias,conditions in which electrical impulses within the heart vary from thenormal rate or rhythm of a heartbeat. The most common arrhythmia isatrial fibrillation (AF), which is characterized by rapid, disorganizedcontractions of the heart's upper chambers, the atria. AF results fromabnormal electrical impulses propagating through aberrant myocardialtissue pathways, which leads to ineffective pumping of the blood throughthe heart, as well as other complications. Atria flutter (AFL), anothertype of arrhythmia, is characterized by a rapid beating of the atria.Unlike AF, AFL arises from a single electrical wave that circulatesrapidly throughout the right side of the heart. Since this arrhythmiacan arise from multiple electrical sites, effective treatment requireselectrical isolation of the aberrant signal sites, thereby forcing theheart's normal conduction pathway to take over.

The practice of interventional electrophysiology for treatingarrhythmias, such as AF and AFL, generally involves insertingspecialized catheters into a patient's vasculature and navigating thedistal (or “working”) end of the catheters into the patient's heartchambers to identify (or “map”) the locations of heart tissue that are asource of the arrhythmias. The mapping of the heart's electricalactivity is typically accomplished using one or more pairs ofelectrodes, each pair spaced apart axially along the working end of thecatheter. Following or in conjunction with the mapping procedure, theattending physician may use an ablation catheter to disable (or“ablate”) the tissue containing the aberrant signal(s) or signalpathway(s), thereby restoring the heart to its normal rhythm.

While catheters may be provided with combined mapping and ablationfunctionalities, separate mapping and ablation catheters are moretypically used, which allows for much greater capability of theirrespective functions. For example, electrical activity is normallymapped using much smaller electrodes (in surface area) than are used forperforming ablation procedures. Because there is significantly lesscurrent transmitted through a mapping electrode circuit than through anablation circuit, the lead wires that connect the mapping electrodes toprocessing circuitry (e.g., via a pin connector in the catheter handle)are much smaller than are used to couple ablation electrodes to an RFgenerator. As such, a much greater number of electrodes may be providedon a mapping catheter than on an ablation catheter having a same orsimilar profile.

For AFL mapping procedures (as well as for some AF procedures), it isimportant to map the electrical activity in both the coronary sinus (CS)and the right atrium (RA), especially the region of the high rightatrium (HRA). Currently, to map both the CS and the RA, a pre-shaped,non-steerable, mapping catheter having two sets of electrodes isinserted through a jugular vein at the base of the patient's neck,through the superior vena cava (SVC), and into the RA, where it bends(or “banks”) off of the lower portion of the atrial chamber (i.e., overthe isthmus region) and into the CS. While functional for mapping therespective RA and CS, this type of catheter has certain drawbacks. Forexample, because it passes across the lower atrial chamber, maneuveringthe mapping catheter for achieving proper electrical contact in the HRAcan be difficult. Further, since most ablation catheters used for AFLand AF interventional procedures are inserted through the groin andinferior vena cava (IVC), and are maneuvered to ablate tissue in theisthmus region of the lower atrial chamber, the mapping catheterextending across the isthmus can block and interfere with the ablationcatheter. Plus, the patient and attending physician must cope withhaving two different access ports into the patient's venous system(i.e., both through the jugular and through the groin), makingsimultaneous control of the respective mapping and ablation cathetersmore difficult, and increasing the chances of related complications andpatient discomfort. While there are diagnostic catheters available formapping the RA and HRA through groin access and the IVC, these typicallyform a complete distal end loop that encircles the atrial chamber, witha small tail segment for slight penetration into the ostium of the CS.The loop portion extends over the isthmus region in the lower rightatrium (LRA), interfering with the ablation catheter, and the limitedpenetration of the CS results in corresponding limited CS mapping data.

Thus, it would be desirable to provide a diagnostic catheter that may bebetter positioned for mapping both the HRA and the CS, which is insertedthrough the groin and IVC, without blocking the isthmus.

SUMMARY OF THE INVENTION

In accordance with one embodiment, an electrophysiology catheterincludes an elongate flexible shaft having a steerable distal sectionand a prolapsing section located proximally of the distal section. Afirst set of electrodes are carried on the steerable distal section, anda second set of electrodes are carried on the prolapsing section. By wayof example, the electrophysiology catheter may be a diagnostic catheter,with the first and second sets of electrodes comprising respective firstand second sets of mapping electrode pairs.

The catheter shaft comprising a soft outer tubing that has an embeddedreinforcing braid extending from the handle through a main body sectionof the catheter to increase its hardness. The reinforcing braidterminates in a transition region between the main body section and theprolapsing section, so that the outer shaft of the prolapsing section ismuch softer, facilitating its prolapsing against the HRA. The distalsection may be steered bi-directionally by actuating pull wires (e.g.,using a steering mechanism in the catheter handle) having distal endsattached to opposing sides of a flat, resilient center support memberpositioned in an interior of the distal section. The steering assemblyalso includes a tightly wound, highly flexible compression coil thatextends from the handle to the support member through a central lumen ofthe outer shaft, with the pull wires positioned within an inner lumen ofthe flexible coil. To facilitate prolapsing of, and provide structuralsupport to, the prolapsing section, the cross-section of the compressioncoil changes from generally circular to generally oval or “flattened”within the prolapsing section, prior to the transition to the distalsection.

In accordance with another embodiment, a method of mapping conductivepathways in a patient's heart tissue includes the steps of (i) insertingan elongate flexible catheter through an access location proximate thepatent's groin and into a patient's venous system, (ii) advancing thecatheter through the patient's inferior vena cava and into the rightatrium, (iii) directing a steerable distal section of the catheter intothe coronary sinus, and (iv) further advancing the catheter to cause aprolapsing section thereof located proximally of the distal section toprolapse against the high right atrium. The method may further includeone or more of (v) applying a back-steering force to anchor the distalsection in the coronary sinus prior to further advancing the catheter tocause the prolapsing section to prolapse against the HRA wall, (vi)mapping electrical pathways in the patient's coronary sinus using one ormore electrode pairs carried on the distal section, and (vii) mappingelectrical pathways in the patient's high right atrium using one or moreelectrode pairs carried on the prolapsing section.

Other and further features and advantages of embodiments of theinvention will become apparent from the following detailed description,when read in view of the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example and notlimitation in the figures of the accompanying drawings, in which likereferences indicate similar elements, and in which:

FIG. 1 is a perspective image of a distal end portion of a diagnosticmapping catheter constructed according to one embodiment.

FIG. 2 is a perspective image of the catheter of FIG. 1 with an internaldistal steering support member being deflected to form a curved loopsegment out of the catheter distal end.

FIG. 3 is a schematic image of the catheter of FIG. 1.

FIG. 3A is a cross-sectional end view taken along dashed line A-A inFIG. 3.

FIG. 3B is a cross-sectional end view taken along dashed line B-B inFIG. 3.

FIG. 3C is a cross-sectional end view taken along dashed line C-C inFIG. 3.

FIG. 4 is a perspective view of the catheter of FIG. 1 extending throughthe respective inferior vena cava and right atrium, and into thecoronary sinus of a three dimensional model of a human heart, with aprolapsed section of the catheter shown slightly torqued and leveragedagainst the wall of the high right atrium.

FIG. 5 and FIG. 6 are additional perspective views of the catheterpositioned in the heart model of FIG. 4.

DETAILED DESCRIPTION

FIG. 1 depicts a distal portion of a diagnostic catheter 20 constructedin accordance with one embodiment of the invention. The catheter 20comprises an elongate, flexible shaft 21 extending from a proximalhandle (not shown), as is well-known in the art for electrophysiologycatheters. The catheter shaft 21 generally includes a steerable distalsection 22, and a prolapsing section 24 located immediately proximal ofthe distal section 20, which distal and prolapsing sections 22 and 24are sized and configured for placement in a patient's coronary sinus(CS) and high right atrium (HRA), respectively. As best seen in FIG. 3,the catheter 20 is a “twenty pole” catheter, with ten electrodes 28(comprising five electrode pairs 30) carried on the steerable distalsection 22 for mapping in the CS, and another ten electrodes 29(comprising five electrode pairs 32) carried on the prolapsing section24 for mapping the HRA. The electrodes 28, 29 are coupled to respectivelead wires that extend through the interior of the catheter shaft andare preferably bundled together (reference no. 36 in FIGS. 3A-3B) in awell-known manner.

In accordance with one aspect of the invention, the catheter shaft 21 issized and configured for accessing the venous system through thepatient's groin, and for navigation up the inferior vena cava (IVC)(reference no. 48 in FIGS. 4-6) and into the right atrium. Using astandard bi-directional steering support member embedded in the distalsection 22 (described below in greater detail), the distal section 22 isguided into the CS. By way of illustration, FIG. 2 shows the distalsection 22 of the catheter shaft 21 formed into a three-quarter loop 25by tensioning of the steering member. As seen in FIGS. 4-6, once thecatheter distal section 22 is positioned in the CS 44, the physicianapplies a “back steering” force on the steering mechanism so that thedistal section 22 will become anchored in the CS 44. The catheter 20 isthen pushed forward by the physician to cause the prolapsing section 24to “prolapse” in an arching loop lying against the wall of the HRA 46.It will be appreciated that the prolapsing section 24 is slightlytorqued (best seen in FIG. 6) as the distal section 22 positioned in theCS is not in the same plane as the prolapsing section 24 lying acrossthe HRA wall, which provides a more stable positioning of the prolapsingsection 24.

With reference to FIGS. 3, 3A, 3B, and 3C, the steering assemblyincludes a flat, resilient center support member 40 positioned in aninterior of the catheter distal section 22. The support member may beactuated using a well-known steering mechanism (not shown) in the handleby a pair of pull wires 34 having distal ends secured on opposing sidesof the steering member 40. As seen in FIG. 3A, a “flattened”Kevlar-reinforced tube 42 is used to constrain the steering wires 34against the center support member 40.

By way of non-limiting example, the steering assembly in the diagnosticcatheter 20 may be similar or identical that used in the Blazer cathetermanufactured and distributed by Boston Scientific(www.bostonscientific.com).

The catheter shaft 21 comprises a relatively soft outer tubing 33 withan embedded braid 31 extending through the main body section 26. Thebraid 31 terminates in a transition region 50 between the main bodysection 26 and the prolapsing section 24, so that the outer tubing 33 ofthe shaft 21 in the prolapsing section 24 is relatively soft (e.g., witha hardness of approximately 35 D in one embodiment) compared to shaft ofthe main body section 26 (e.g., with a hardness of approximately 72 D inone embodiment). The relatively soft outer shaft enables the prolapsingsection 24 to readily prolapse into the HRA when the distal section isanchored in the CS. The stiffer outer shaft 33 of the main body section26 also facilitates prolapsing of the prolapsing section 24 against theHRA wall.

A cross section of the prolapsed section 24 is preferably substantiallycircular about its outer diameter. Residing in an interior lumen 39 ofthe outer tube 33 is a tightly wound, flexible compression coil 38 thatconstitutes part of the steering assembly. The coil 38 also provides ahighly flexible structure for facilitating prolapsing of the prolapsingsection 24 into (and against the wall of) the HRA. The coil 38 may bemade of a stainless steel and preferably extends throughout the catheterbody 21, i.e., from the handle to the center support member 40 in thedistal section 22. The cross-section of the coil 38 preferably changesfrom a substantially circular shape in the main body section 26 to asubstantially oval or flattened shape in the transition region 50between the main body and prolapsing sections 26 and 24 in order providedirectionality and enhanced torque of the prolapsing section 24. A hingejoint (not shown) may optionally be built into a transition region 52located between the prolapsing section 24 and distal section 22, tofurther facilitate prolapsing of the prolapsing section 24 against thewall of the HRA.

It will be appreciated that the diagnostic catheter 20 will typically beused in conjunction with AFL ablation procedures in order to accessbi-directional block across the isthmus, without interfering with theablation catheter during the creation of an isthmus lesion. The catheter20 may also be used for AF procedures, where it is important for thephysician to map the electrical activity in the CS as well as the HRA.Because the catheter 20 is positioned through groin access and the IVC,and in particular because the prolapsing section 24 is torqued againstthe wall of the HRA, maneuvering for achieving solid electrical contacton the wall of the HRA is much easier than in previously existing RAmapping catheters.

The forgoing illustrated and described embodiments of the invention aresusceptible to various modifications and alternative forms, and itshould be understood that the invention generally, as well as thespecific embodiments described herein, are not limited to the particularforms or methods disclosed, but to the contrary cover all modifications,equivalents and alternatives falling within the scope of the appendedclaims.

What is claimed is:
 1. An electrophysiology catheter, comprising: an elongate flexible shaft having an inner lumen, a steerable distal section, and a prolapsing section located proximally of the distal section, with a soft outer tube extending from a proximal end of the prolapsing section to a distal end of the steerable distal section; a resilient center support member positioned in the inner lumen of the distal section; a plurality of steering wires disposed in the inner lumen, wherein distal ends of the wires are secured to the center support member in the distal section, such that the distal section itself may be steered bi-directionally about the resilient center support member; a first plurality of electrodes carried on the steerable distal section; and a second plurality of electrodes carried on the prolapsing section. 